(Unlike TTTM has mentioned as ranging from 1/1000th of a second to 5 minutes.) TTTM, 5 minutes are called 5 MINUTES, not jiffy. May be 5 minutes are jiffy for your age, but certainly its not the definition.

The unit of time that is one jiffy cannot be defined relative to other units of time, it is separate, disassociated and different from the way other units are measured and experienced and cannot therefore be explained it terms of amount of time. For jiffy is time, in its raw form and is not like anything that we as humans can comprehend!

Thor: I'll be there in a jiffy.
Inconspicuous looking egg: That does not give me any indication as to how long you are going to be as jiffy is an indefinable period of time.